A circular stapling instrument (100D) is provided which includes a reciprocating drive shaft (114D) and a firing bar (282D). The reciprocating drive shaft has a first engagement member (244D) at a tip of the reciprocating drive shaft and a threaded adjustment member (286D) at a base of the reciprocating drive shaft. The firing bar is movably connected at a first end with a firing trigger (122D) and movably connected at a second end with a stapling head assembly through a second engagement member. The firing bar forms a first engagement surface which faces a respective second engagement surface formed on the reciprocating drive shaft. The circular stapling instrument also includes a frictional reducing member (420D) located in between the first and second engagement surfaces in order to reduce friction between the reciprocating drive shaft and the firing bar.
